Fabrication Of Soy Protein Nanoparticles Through Controllable Enzymatic Hydrolysis:Towards Modulating Lipid Digestion In Emulsions

Food protein-stabilized emulsion is one of the most important systems in Food industry,which is also the main existence form of lipids in processed foods.Recent studies indicated that modulation the digestion processes of protein-stabilized emulsion to reduce the lipid absorption was an efficient approach to control the energy intake from food.Compared with natural proteins,the emulsion prepared with protein nanoparticles,namely Pickering emulsion,owns apparent advantage in the aspects of stabilizing emulsion and retarding lipid digestion,exhibiting tremendous application foreground in low-calory emulsion foods.Thus,how to produce food protein colloidal particles with high emulsifying capacity in the preparation of Pickering emulsion with efficient regulation of lipid digestion through more effective and sustainable way has become a hotspot in the field of modern healthy emulsion food.According to this,this essay used soy protein isolate(SPI)that belonged to bulk plant protein resource as raw material,and successfully fabricated soy protein nanoparticles(SPNP)with controllable structures and functions by employing steerable biological enzymatic hydrolysis technology,followed with the systematic measurements and analyses of the structure characteristics and formation mechanism of SPNP.Afterthat,Pickering emulsions were further prepared using SPNP as interface stabilizers,and their role in the modulation of lipid digestion and mechanisms involved were investigated.The main research contents and conclusions of this essay are as followed:1.Eight enzymes were separately used to treat SPI,and dynamic light scattering(DLS)technology was applied to preliminarily explore the formation of SPNP.Flavorzyme,Alcalase and Protamex were selected to prepare soy protein hydrolysates with hydrolysis degree(DH)of 3%,7% and 11% to systematically explore the influence regularity of different enzymes and DH on the formation and structures of SPNP.As the results showed,the formation of SPNP highly depended on the enzyme type and DH condition.SPNP could be fabricated by Flavorzyme at all DH conditions,while SPNP could be formed only at 3% DH by Protamex.All SPNP were homogeneously spherical with average size at 80-170 nm,and their structures were predominantly maintained by hydrophobic interactions,with hydrogen bonds and disulfide bonds primarily located at their external and internal structures,respectively.As the results from SDS-PAGE and CD shown,most SPNP retained the complete subunits of 7S and 11 S globulins,meanwhile showing specific ratio of ?-helix/?-sheet(around 45%).Besides,the enhancement of surface hydrophobicity and the generation of antioxidant small peptides during the hydrolysis of ??? subunits also endowed SPNP with superior antioxidant activity.2.The interfacial absorption behavior and wettability at oil-water interface of SPNP were further studied,followed with the preparation of oil-in-water(O/W)Pickering emulsions and exploration of the influence of SPNP on their formations and stabilities.As the results exhibited,the SPNP fabricated under low DH with small size,high surface hydrophobicity could fast absorb to the oil-water interface,and partially refolded at interface.Except the SPNP with subunits terribly degraded showing hydrophilic three contact angle(? = 53.45°),the hydrophilicity and lipophilicity of other SPNP were similar(? close to 90°).Both the size and wettability of SPNP had obvious effects on the physical stability of Pickering emulsions: the SPNP with large size enhanced the interface thickness of emulsion and further impove the storage stability(anti-coalescence)and lipid oxidation stability,meanwhile triggering emulsion flocculation.The hydrophilic SPNP displayed limited emulsifying activity and emulsion storage stability;the SPNP with similar hydrophilicity and lipophilicity demonstrated outstanding emulsifying activity,emulsion strorage stability and lipid oxidation protection capability.3.The SPNP formed under 3% DH were taken as the interfacial stabilizers,and their role in the modulation of lipid digestion in Pickering emulsions and mechanisms involved were researched.As the results displayed,SPNP still existed at the emulsion interface with form of particles and showed pleasurable ability on the anti-absorption or displacement of bile,indicating the potential of the O/W interfaces stabilized by SPNP in the delay of lipid digestion.The simulated digestion of Pickering emulsions were further carried out by applying gastrointestinal digestion model,and the initial digestion rate and final digestion degree of lipid during those processes were studied.As the results shown,all SPNP decreased the release rate and degree of FFA in Pickering emulsions with varied abilities,of which the SPNP prepared by Protamex exhibited the best capability in controlling lipid digestion,due to its deformation at the O/W interface and the resulted increased coverage area.Compared with SPI,this Pickering stabilizer reduced the initial digestion rate by 73..88% and the final digestion degree by 15.13%.The results from SDS-PAGE and CLSM indicated that this SPNP could resist against the hydrolysis of pepsin at emulsion interface,whilst the Pickering emulsion prepared displayed superior anti-coalescence stability during the gastrointestinal digestion.